May be the guy loves his wife for real. For a lot of people, age difference makes no difference. Or may be he is just waiting to receive his residency card to live the girl. That way he does not have to tell anyone in his family that he ever got married to her. Keep the secret for a while until residency card.
But the girl is also at fault here. Why did she get married to a guy who wants to keep the marriage secret from his family? Isn't that a big red flag?